Remote treatment of wells



Dec. 20, 1966 w. F. MILLER 3,292,704

REMOTE TREATMENT OF WELLS Filed June 12, 1963 United States Patent 9 3,292,704 REMOTE TREATMENT OF WELLS William F. Miller, Ventura, Califi, assignor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed June 12, 1963, Ser. No. 287,254 4 Claims. (Cl. 166-91) The present invention relates to the production of petroleum from subsurface wells and, more particularly, is concerned withthe treatment of such wells and well equipment to maintain effective and efiicient operation.

A producing well or its well head equipment may frequently require treatment to assure that the well or the well head equipment and particularly the delivery lines remain unobstructed and in serviceable condition. In the case of submarine installations, which are of increasing significance, access to the well or the Well head for this purpose is not readily available.

For example, the well head equipment, including an arrangement commonly known as the Christmas tree involving valves, ducts and control elements of the system, may be located near the bottom of a body of water and, in any event, substantially below the surface with the flow lines and other conduits laid on the bottom to a delivery point on shore or at some other convenient location such as a working platform. The control equipment, and particularly the well head valves, being normally inaccessible for manual operation, are typically hydraulically actuated from a remote location. All of this, together with equipment to enable workover, maintenance and well treatment, may provide an inordinate complexity of equipment and lines.

The present invention obviates this in substantial measure by providing for controlled admission of treatment fluid to the well head through the agency of one or more of the hydraulic control lines, which serve also to carry the hydraulic control fluid for pressuring the hydraulic actuators which are connected to the well head to control the valves and other mechanically actuable elements of the well head equipment. This obviates at least one necessary line to the producing well. Moreover, since the treatment fluid ordinarily may also function as a suitable hydraulic control fluid, separate supplies of fluid are unnecessary.

This is accomplished by conduct ng the treatment fluid from an existing hydraulic control line to the appropriate point of injection into the well head equipment by way of a branch line or conduit provided with a pressure-release or back-pressure valve which opens at a predetermined pressure of the fluid, substantially in excess of the pressure required to actuate the well head controls.

As a result, the injection equipment remains inoperative throughout normal operation of the hydraulically actuated well head controls but is selectively brought into operation by application of a predetermined pressure to the hydraulic pressure line in excess of ordinary actuating pressures. At this time, under the influence of the excess pressure, the back-pressure valve opens to admit a predetermined quantity of treatment fluid into the well head equipment.

By way of example, the present invention is particularly advantageous in the control of wax or paraffin deposition, characteristic of many producing wells and the associated flow lines. By paraffin or wax, as used herein, is meant the paraflinaceous or other residual materials which tend to deposit on the interior walls of flow lines as the produced petroleum flows from the relatively higher temperature and pressure environment of the producing formation during production. Selective introduction of a wax solvent is one effective means for dissolving and removing such deposits.

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However, the treatment fluid is not so limited but it may include any fluid applicable to treatment of such equipment or flow lines or the well itself such as, for example, inhibitors, corrosion prevention materials or any well-known well or formation treating agents. For instance, the treating fluid may involve a fluid treatment agent which, as distinguished from a solvent, is injected into the well to prevent the adherence of waxy or other deposits on the flow lines, as that contemplated by US. Patent 2,927,078. Alternatively, the present invention is useful for the injection of alcohols or glycols such as are typically used to prevent ice or hydrate formation on wet gas lines.

The invention will be more readily understood by reference to the drawing which discloses more or less diagrammatically, in elevation, one typical embodiment thereof.

In the drawing, a well head or so-called Christmas tree assembly is mounted upon a surface tubing or conductor casing 14. As indicated, the well head equipment contemplated by the invention is preferably a submarine assembly located below the surface of a body of Water and ordinarily close to the bottom as indicated by the numeral 12.

The conductor or surface casing 14, as is known, extends a substantial distance into the relatively unconsolidated formation and is cemented into place as diagrammatically indicated at 16. The well head body 18 is landed on the upper end of the conductor 14 as indicated and secured or fastened thereto by any convenient means. Inasmuch as this fastening may be accomplished by welding, bolting or by a releasable connection, all of which are known in the art, details are not shown. One known form of connection, for example, comprises an interlocking structure which can be attzllched or released by remote hydraulic pressure contro A well casing 24) normally extending downwardly at least to the vicinity of the producing formation, is engaged with and hung from the well head body 18 by easing hanger 22. The casing hanger comprises slips and packing units and which, as is known, grip the upper end of the casing, and at the same time engage a corresponding tapered surface 24 in the well head body 18. A string of production tubing 25, that is to say the conduit which ordinarily carries the produced oil to the surface, is similarly suspended at its upper extremity by tubing hanger 26 which also engages in tapered section 28 of well head body 18.

A locking mandrel 30 with a central passageway 32 which forms a continuation of the production tubing 25, closes the upper extremity of the well head body 18 and again may be secured in place by any convenient releasable means not shown.

Landing mandrel 34 coaxially received in the upper end of locking mandrel 30 is connected to a tubing nipple 36 which leads to the inlet part of master valve 38. The outlet of valve 38 in turn is connected by an axially aligned nipple 40 to a production cross fitting 42 which in turn is connected by nipple 44 to the lower part of swab valve 46. The upper swab valve port in turn receives nipple 48 which is closed by cap fitting 50.

The produced well fluid coming up the production tubing normally passes through nipple 36, valve 38 and nippie 4% into the cross fitting 42 from which it passed into laterally extending production line 52. This, in turn, leads to the delivery point on shore or at another suitable terminal point not shown.

The other side of cross fitting connects with a laterally extending conduit or pipe 54 which, for example, may comprise a pigging line. Among the purposes served by the pigging line is that of providing for the passage of pig orscraper, driven by pressure through the cross and the production line 52 at intervals to remove wax, scale and deposits. A wing valve and hydraulic actuator indicated diagrammatically by reference 56 is provided .in pigging line 54. A similar valve may be provided in ffiow line 52 although this function may be taken over by suitable controls at the delivery terminal.

Valves 33 and 46 are actuated and controlled by hydraulic actuators 58 and 60 respectively and valve 56 is provided with a similar actuator not specifically visible in the present view. Pressure control of these actuators is efl'ected by pressure line 62 coming from any suitable remote control point to the respective actuating device. For this purpose T-fittings 64, 66 and 68 connect through branch lines 70, 72 and 74 with the respective actuators.

In accordance with the present invention an extension or branch line 76 of conduit 62 leads to adjustable pressure-relief or back-pressure valve 78 which in turn connects to conduit-80 which enters the afore-mentioned cap 50 on the end of the nipple 48 at the upper end of the well head.

Back pressure valve 78 is not disclosed in detail for I the reason that it takes the form of any of the Wellknown type of valves which are normally closed to the passage of fluid but which open at a predetermined pressure on the inlet to permit free flow of the fluid. Preferably, the opening pressure may be pre set by means of adjustment handle 82. I

Another important feature of the invention involves a choke or so-called flow bean 84 which is interposed within the branch conduit 80 downstream of valve 78. This involves simply an orifice of predetermined size selected specifically to control the flow of pressure fluid through the line 80 and additionally to reduce the relative pressure drop through the back pressure valve 78.

Preferably the orifice is sized so that the major portion,

and preferably substantially all of the pressure drop in the branch conduit defined by lines 76 and 80 occurs at this point and accordingly maintains a substantial back pressure on valve 78.

Therefore, the flow restrictive orifice. 84 not only enables introduction of quite accurately predetermined amounts of fluid into the well head but prolongs the life of the relief valve and particularly the seating elements thereof. In addition, it tends to assure operation of the relief valve at a preset, predetermined pressure.

In the operation of the present system, valves 38 and 46 are normally closed and valve 56 is normally open in the absence of pressure in the line 62. Valves 38 and 46 are therefore brought to open positions by the respective actuators upon the application of a predetermined pressure. This accordingly assures shut down of the system in the event of hydraulic pressure failure. On the other hand, valve 56 is normally held open by spring action or the like and closes upon the'application of pressure in the hydraulic control line. This permits a scraper pig to be pumped from a central control point through line 54, the production cross 42 and back to the control point through flow line 52, While the valves 38 and 46 are closed and the well is thus shut-in. The valves may be controlled from a remote position at the surface simply by the application or release of the operational pressure to the actuators.

Back pressure valve 78 is set to open at a predetermined pressure substantially in excess of the normal range of operational pressure or pressures for the aforementioned valve actuators. .Therefore, for the purpose of injecting well treating fluid into the well head assembly, the pressure in conduit 62 is raised sufiiciently to open valve 78 whereupon the pressure fluid proceeds to flow from line 62 through line 76, valve 78, orifice 84 and branch line 80 into the upper extremity of the well head. It thereupon flows downwardly past valve 46 and may pass through cross fitting 42 into flow'line 52.

however, flow line 52 is closed off at the shore by valve means not shown, then treating fluid may tend to pass downwardly through production tubing 25 and into the well itself. Ordinarily the presence of gas in the produced 011 permits this, enabling the treatment fluid to penetrate down the production tubing a substantial dis tance, for example, to a level below the point of incipient parafiin deposition.

tion tube results.

Actually, it will be apparent that by application of a pressure sufficiently above the well pressure itself the treatment fluid may be forced down the production tubing 25 to any desired extent and even into the producing formation itself.

In the treatment of the lines for wax removal the pressure line 62 is supplied with suitable parafiin solvent which also may be suitable for pressuring the respective actuating means. For example, it may comprise a natural gasoline fraction, a light naphtha preferably with a substantial aromatic cut, LPG, carbon tetrachloride, carbon This, obviously in flowing through disulfide or the like. the various conduits such as cross connector 42 into flow line 52, tends to dissolve and clear away any paraffinaceous deposits. When production is re-established, the dissolved residue is carried away with the produced oil.

The treatment fluid may, of course, be introduced at any other convenient point in the well head or the well head equipment, by which is meant the well head and.

all of its associated ducts. For example, in place of the branch line injection conduit there may be provided alternatively, a conduit indicated by the dashed line 86 through the line 52 may be restricted during injection of the paraflin solvent and then shut off so that the injected solvent is permitted to remain in place for a suflicient time to effect complete dissolution of the waxy deposits. Thereafter production is continued. I V

A yet further modification of the present invention contemplates injection of the treatment fluid through pasa sageway 88 into the annular space. In other words, the annular passage between the casing 20 and the production tubing 25 may provide a conduit extending to the lower reaches of the well which is normally kept full of the treatment agent. Ordinarily a packer 92 closes the annulus near the lower end of the casing 20 and therefore the wall of the tubing 25 may be provided above the packer with a back pressure valve opening between the annulus and the interior of the tubing 25. Because such so-called injection valves are well known in the art, no detailed description thereof is believed necessary- Such an arrangement is particularly useful for the chemical treatment of a well with corrosion inhibitor or the like.

In any event,.the present invention permits the controlled injection of treating fluid into the well or any of its adjunctive conduits or chambers, by way of existing control lines.

Obviously many modifications and variations of the invention as set forth in the foregoing illustrative embodiments, may be made without departing from the spirit and scope thereof, and only such limitations should be imposed as are indicated in the appended claims.

By maintaining the well closed inv until solution of the paraffin is completed a clean produc- I claim:

1. In a well head assembly associated with a subsurface well and comprising well head equipment including at least one flow line extending from the well and bydraulically actuated control means for controlling the flow of fluid from the Well, a pressure line for controlling said hydraulically actuated control means in response to application of control pressures to said pressure line and means for introducing a well treatment fluid into said flow line, said last mentioned means comprising means for supplying a well treatment fluid under pressure to said pressure line, a branch conduit extending from said pressure line into said flow line, and means normally closing said last mentioned branch conduit but operable at pressures above said control pressures to open said conduit to the passage of fluid.

2. In a well head assembly associated with a subsurface well having at least one flow line extending from the well for conveying well fluid, and having a hydraulic actuating means for controlling the flow of fluid from the well and a fluid pressure line connected to said hydraulic actuating means for actuation thereof from a relatively remote point in response to the application of predetermined controlled pressures to said fluid pressure line, means for introducing a predetermined amount of well treatment fluid into said flow line at a predetermined location, said last mentioned means including means for supplying the well treatment fluid to said fluid pressure line under controlled pressure, a bypass conduit extending from said fluid pressure line into said flow line at said predetermined location and normally closed backpressure valve means located in said bypass conduit and operable to open at pressures of said well treatment fluid in said fluid pressure line above a predetermined minimum pressure which minimum pressure is above said control pressures to allow passage of said well treatment fluid through said bypass conduit.

3. A well head assembly as called for in claim 2, Wherein the bypass conduit is provided with a flow restriction orifice downstream of the said back-pressure valve.

4. A well head assembly as called for in claim 3, wherein said flow restriction orifice is adapted to eflfect a major portion of the pressure drop in the bypass conduit and thereby substantially reduce the pressure drop through said back-pressure valve.

References Cited by the Examiner UNITED STATES PATENTS 2,047,414 7/1936 Henry et al 16675 X 2,163,436 6/1939 Raymond et a1. 16675 3,053,320 9/1962 Steincamp 16675 X 3,211,225 10/1965 Thiessen et al 16675 3,228,472 1/ 1966 Rhoads 16675 X CHARLES E. OCONNELL, Primary Examiner.

T. A. ZALENSKI, Assistant Examiner. 

1. IN A WELL HEAD ASSEMBLY ASSOCIATED WITH A SUBSURFACE WELL AND COMPRISING WELL HEAD EQUIPMENT INCLUDING AT LEAST ONE FLOW LINE EXTENDING FROM THE WELL AND HYDRAULICALLY ACTUATED CONTROL MEANS FOR CONTROLLING THE FLOW OF FLUID FROM THE WELL, A PRESSURE LINE FOR CONTROLLING SAID HYDRAULICALLY ACTUATED CONTROL MEANS IN RESPONSE TO APPLICATION OF CONTROL PRESSURES TO SAID PRESSURE LINE AND MEANS FOR INTRODUCING A WELL TREATMENT FLUID INTO SAID FLOW LINE, SAID LAST MENTIONED MEANS COMPRISING MEANS FOR SUPPLYING A WELL TREATMENT FLUID UNDER PRESSURE TO SAID PRESSURE LINE, A BRANCH CONDUIT EXTENDING FROM SAID PRESSURE LINE INTO SAID FLOW LINE, AND MEANS NORMALLY CLOSING SAID LAST MENTIONED BRANCH CONDUIT BUT OPERABLE AT PRESSURES ABOVE SAID CONTROL PRESSURES TO OPEN SAID CONDUIT TO THE PASSAGE OF FLUID. 